A. Field of the Invention
This invention relates to tall pole assemblies having a carrier for luminaires or the like which can be raised or lowered and, in particular, to a system for visually indicating when the carrier makes contact with the top portion "masthead" of said pole.
B. Prior Art
Systems are known in which carriers of luminaires or the like are transported upwardly or downwardly about a tall pole. Conventionally, the carriers are lowered and raised by a plurality of cables attached to the carrier which pass over pulleys in the top portion (masthead) of the pole and thence pass downward through the pole for connection to a single winch cable as shown in my U.S. Pat. No. 4,149,230, granted Apr. 10, 1979. Latching mechanisms on the carrier and masthead which are mutually engageable operate to suspend the carrier from the masthead when the carrier is raised to its proper position at the top of the pole.
When maintenance is required for the luminaires, the winch unreels its cable thereby unlatching the carrier and permitting the cables suspending the carrier to lower the carrier. When the carrier is again raised by reverse winch action, the carrier rises until its latching mechanisms reengage the cooperating mechanisms on the masthead. The latching mechanisms rather than the suspensory action suspend the carrier as otherwise the cables would be called upon to bear too heavy a load for too long a time between maintenance calls. It is important for safety as well as other reasons that the operator of the winch know when the carrier has engaged or been freed of its latching engagement with the top portion of the pole respectively on its way up or down the pole.
In the past, judgement of the position of the carrier relative to the top of the pole has often been a matter of the acuity of the visual perception of the winch operator. But such perceptions can, at the distances involved, sometimes be erroneous with the possible result that undue tension may be placed upon one or more of the cables thereby elongating them relative to the others. Sometimes the winch operator, thinking that the carrier has been placed in its latched-in position, mistakenly relaxes the winch cable whereupon the carrier falls to the ground.
In order to prevent this, some visual indicating systems are known in the art. For example, in the aforesaid U.S. patent, a system is shown and claimed in which the carrier is provided with a spring-loaded, shock-absorbing suspensory cable termination system. The system operates such that only when the plurality of the carrier latching mechanisms are engaging their cooperating latching mechanisms in the masthead do brightly-colored terminations on the suspensory cables become visible from below. This system, while effective for its intended purpose, may sometimes be more expensive than is economically feasible for a given installation.
Another system known to the art is described in U.S. Pat. No. 3,911,267 issued Oct. 7, 1975 in which the carrier bears a colored movable disc or signal mounted on an arm for movement about a horizontal pivot. It normally is biased so that when the carrier is lowered or not at its maximum upward position, the disc is angled upward so that the disc is barely visible or appears, at best, elliptical in shape. When the carrier is at its maximum upward position, the signalling arm is urged by contact with the masthead into a substantially horizontal position whereupon the disc appears as essentially round to the ground observer. It is conceivable that ground observers with ocular defects possibly could misconstrue a full circle as being an ellipse or vice-versa.
It is believed that the present system, being quite simple and relatively inexpensive as well as substantially maintenance-free offers considerable advantages over prior art systems in certain applications.